Effect of rapid thermal annealing on the characteristics of amorphous carbon/n-type crystalline silicon heterojunction solar cells

Abstract

Heterojunction solar cells were fabricated by the deposition of un-doped amorphous carbon on mono-crystalline n-type silicon wafer (a-C/Si) using a frequency doubled pulsed Nd:YAG laser under vacuum followed by rapid thermal annealing (RTA). Structural and optical properties were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX), atomic force microscopy (AFM), Fourier transformation infrared spectroscopy (FTIR), and UV–vis transmittance. Optical properties investigation showed a 2.2eV optical band gap of the amorphous carbon. I–V characteristics indicated a good rectification of the a-C/Si heterojunction with an ideality factor of 3. The 30s annealed a-C/Si solar cell at 600°C showed the highest conversion efficiency (η=1.1%). The maximum open circuit voltage (Voc) and short circuit current density (Jsc) of the cells were 250mV and 33.3mA/cm2 respectively. The photo-response of the cells was significantly improved after RTA.